This invention relates generally to a sound image processing system for positioning audio signals reproduced over headphones and, more particularly, for causing the apparent sound source location to move in azimuth, range and elevation relative to the listener with smooth transitions during the sound movement operation.
Due to the proliferation of sound sources now being reproduced over headphones, the need has arisen to provide a system whereby a more natural sound can be produced and, moreover, where it is possible to cause the apparent sound source location to move as perceived by the headphone wearer. For example, video games both based on the home personal computer and based on the arcade-type games generally involve video movement with an accompanying sound program in which the apparent sound source also moves. Nevertheless, as presently configured, most systems provide only a minimal amount of sound movement that can be perceived by the headphone wearer and, typically, the headphone wearer is left with the uncomfortable result that the sound source appears to be residing somewhere inside the wearer""s head.
A system for providing sound placement during playback over headphones is described in U.S. Pat. No. 5,371,799 issued Dec. 6, 1994 and assigned to the assignee of this application, which patent is incorporated herein by reference. In that patent, a system is described in which front and back sound location filters are employed and an electrical system is provided that permits panning from left to right through 180xc2x0 using the front filter and then from right to left through 180xc2x0 using the rear filter. Scalars are provided at the filter inputs and/or outputs that adjust the range and location of the apparent sound source. This patented system requires a large number of circuit components and filtering power in order to provide realistic sound image placement and in order to permit movement of the apparent sound source location using the front and back filters, a pair of which are required for the left and right ears.
At present there exists a need for a sound positioning system for use with headphones that can create three-dimensional audio imaging without requiring complex and expensive filtering systems, and which can permit panning of the apparent sound location for one or more channels or voices.
These and other objects, features and technical advantages are achieved by a system and method which provides an apparatus for creating three dimensional audio imaging during playback over headphones using a binaural synthesis approach.
It is another object of the present invention to provide apparatus for processing audio signals for playback over headphones in which an apparent sound location can be smoothly panned over a number of locations without requiring an unduly complex circuit.
It is another object of the present invention to provide an apparatus for reproducing audio signals over headphones in which a standardized set of filters can be provided for use with a number of channels or voices, so that only one set of filters is required for the system.
It is another object of the present invention to provide an apparatus for processing audio signals for playback over headphones, for causing the apparent sound source location to move in elevation relative to the listener with smooth transitions during the sound movement operation.
In accordance with an aspect of the present invention, the apparent sound location of a sound signal, as perceived by a person listening to the sound signals over headphones, can be accurately positioned or moved using front and back azimuth placement filters, elevation placement filters, early reflection filters, and a reverberation filter. The inputs to the filters are controlled using variable attenuators or scalars that are associated with each input signal and not with the filters themselves.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.